Since polyarylene sulfide (hereinafter abbreviated as PAS) as represented by polyphenylene sulfide (hereinafter abbreviated as PPS) resin has high heat resistance, mechanical properties, chemical resistance, dimensional stability and fire retardancy, it is widely used for component materials of electrical and electronic equipments, automobile equipments, chemical equipments, and the like.
Meanwhile, from the viewpoint of reduction of environmental load, the demand for the reduction of halogen content of materials is increasing recently. Since PAS resins can be obtained by polymerizing p-dichlorobenzene with alkali metal sulfide or alkali metal hydrosulfide as raw materials, they inevitably have the property of containing chlorine, being a kind of halogen, remaining at the end of the polymers while they don't contain chlorine in the main molecular skeletons. From the viewpoint of the environment problem described above, PAS resins having a low level of contained chlorine are required in the market, but it has been considered technically extremely difficult to provide PAS resins having a reduced chlorine level, excellent molding and processing properties without impairing excellent properties of PAS resins.
Further, since PAS resins have good compatibilities with inorganic fillers, they are generally often used as complex materials with inorganic fillers added. By complexation of materials, the content of chlorine in the form of resin composition can be reduced to some extent, but in consideration of melt flowability and mechanical strength, the addition of inorganic fillers is limited, and thus the request in the market for the reduction of chlorine level cannot be satisfied by using complexation technology alone.
Further, the chlorine concentration in the polymer usually depends on molecular weight of the polymer. Namely, a low-molecular-weight polymer with a high total number of terminals of the molecule has a high chlorine concentration, while a high-molecular-weight polymer with a low total number of terminals of the molecule thereby h has a low chlorine concentration. For that reason, to obtain a PAS resin composition with a low chlorine level, a high-molecular-weight polymer is preferably used as a raw material. Further, PAS resins are divided broadly into two types, thermal crosslinking-type and linear (straight chain)-type by their molecular structures. The thermal crosslinking-type PAS resins generally have a high chlorine concentration as they can be obtained by oxidative crosslinking through the use of a low-molecular-weight PAS resin with a high chlorine concentration as a raw material. To obtain a PAS resin composition with a low level of contained chlorine, the use of linear type PAS resins is preferable.
On the other hand, there may be a problem in which flash tends to occur during injection molding when a linear type PAS resin is used. To solve this problem, conventional methods for adding a variety of alkoxysilane compounds have been known (for example, JP-A 1-89208, JP-A 9-153383 and JP-A 1-146955). However, there is a problem that a high reactivity between a variety of alkoxysilane compounds and PAS resin increases the melt viscosity of the resin, and thus deteriorates flowability.
For the purposes of reduction of chlorine, using high-molecular-weight linear type polymers as a raw material is preferable as described above, but if alkoxysilane is added to solve a problem of flashing defect, flowability decreases, which is not preferable for practical purposes.